#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,a,b,c,d,s;
    cin>>n;
    a=n%10;
    b=n/10%10;
    c=n/100%10;
    d=n/1000;
    s=a+b+c+d;
    cout<<s;
	return 0;
}
/**************************************************************
	Problem: 1390
	User: linyuhang
	Language: C++
	Result: Accepted
	Time:21 ms
	Memory:2072 kb
****************************************************************/